1. Field of the Invention
The present invention relates to a trim and tilt system for use with a propulsion unit mounted on a marine craft.
2. Description of Related Art
Conventional trim and tilt systems include a unitary trim and tilt cylinder apparatus, as disclosed in U.S. Pat. No. 5,032,094, issued Jul. 16, 1991 to Sadaji Katogi, hereinafter Katogi. Katogi discloses a trim and tilt system for trimming and tilting an outboard propulsion unit mounted on a marine craft. The trim and tilt system disclosed by Katogi includes a unitary trim and tilt cylinder apparatus having a tilt cylinder unit and a trim cylinder unit; a stern bracket configured to be mounted on the transom of the marine craft; a swivel bracket for supporting the outboard propulsion unit; the swivel bracket being pivotally supported on an upper end of the stern bracket; and a hydraulic fluid circuit for actuating the tilt cylinder unit and the trim cylinder unit. The trim and tilt cylinder apparatus has an upper end pivotally supported on the stern bracket and a lower end pivotally supported on the swivel bracket.
In the trim and tilt system disclosed by Katogi undue stress may be applied to the trim cylinder units at points of contact between the trim rods and the swivel bracket. This excessive stress is in part due to the unitary construction of the trim and tilt cylinder apparatus. As the outboard propulsion unit pivots during the trimming phase, the angle of the trim rods changes with respect to the swivel bracket. The weight of the propulsion unit is therefore applied to the trim rods at various angles throughout the trimming phase. This may lead to a considerable amount of transverse stress being applied to the trim rods and their respective trim cylinders which, in turn, may lead to undue wear and fatigue.